WICHITA, Kan. – A man suspected of fatally shooting abortion doctor George Tiller in church was in jail Monday while investigators sought to learn more about his background, including his possible connections to anti-abortion groups.

Tiller, 67, was serving as an usher during morning services Sunday when he was shot in the foyer of Reformation Lutheran Church, police said. The gunman fired one shot at Tiller and threatened two other people who tried to stop him.

The suspect, identified by one law enforcement agency as Scott Roeder, was taken into custody some 170 miles away in a Kansas City suburb about three hours after the shooting.

Tiller had been a lightning rod for abortion opponents for decades. The women's clinic he ran is one of three in the nation where abortions are performed after the 21st week of pregnancy, when the fetus is considered viable, and has been the site of repeated protests for about two decades. A protester shot Tiller in both arms in 1993, and his clinic was bombed in 1985.

Roeder, 51, was returned to Wichita and was being held without bail on one count of first-degree murder and two counts of aggravated assault. Formal charges were expected to be filed Monday.

In Washington, the U.S. Marshals Service said that as a result of Tiller's shooting, Attorney General Eric Holder had ordered it to "increase security for a number of individuals and facilities" in the country. Jeff Carter, U.S. Marshals spokesman, said he could not disclose details.

A man with the same name as the suspect has a criminal record and a background of anti-abortion postings on sympathetic Web sites. In one post written in 2007 on the Web site for Operation Rescue, a group that closely followed Tiller's work and legal troubles in recent years, a man identifying himself as Scott Roeder asked if anyone had thought of attending Tiller's church to ask the doctor and other worshippers about his work.

But police said Sunday that all early indications showed the shooter acted alone. Operation Rescue condemned the killing as vigilantism and "a cowardly act." The president of the group told The New York Times that Roeder was "not a friend, not a contributor, not a volunteer."

In 1996, a 38-year-old man named Scott Roeder was charged in Topeka with criminal use of explosives for having bomb components in his car trunk and sentenced to 24 months of probation. However, his conviction was overturned on appeal the next year after a higher court said evidence against Roeder was seized by law enforcement officers during an illegal search of his car.

At the time, police said the FBI had identified Roeder as a member of the anti-government Freemen group, an organization that kept the FBI at bay in Jordan, Mont., for almost three months in 1995-96. Authorities on Sunday night would not immediately confirm if their suspect was the same man.

Morris Wilson, a commander of the Kansas Unorganized Citizens Militia in the mid-1990s, told The Kansas City Star he knew Roeder fairly well.

"I'd say he's a good ol' boy, except he was just so fanatic about abortion," Wilson said. "He was always talking about how awful abortion was. But there's a lot of people who think abortion is awful."

In May 2007, someone posting to the Web site of the anti-abortion group Operation Rescue used the name "Scott Roeder" in response to a scheduled vigil to "pray for an end to George R. Tiller's late-term abortion business."

"Bleass everyone for attending and praying in May to bring justice to Tiller and the closing of his death camp," the posting read. "Sometime soon, would it be feasible to organize as many people as possible to attend Tillers church (inside, not just outside) to have much more of a presence and possibly ask questions of the Pastor, Deacons, Elders and members while there? Doesn't seem like it would hurt anything but bring more attention to Tiller."

The slaying quickly brought condemnation from both anti-abortion and pro-choice groups, as well as President Barack Obama.

"However profound our differences as Americans over difficult issues such as abortion, they cannot be resolved by heinous acts of violence," Obama said in a statement.

Wichita Deputy Police Chief Tom Stolz said that Tiller apparently did not have a bodyguard with him in church, although the doctor was routinely accompanied by one. An attorney for Tiller, Dan Monnat, said the doctor's wife, Jeanne, was in the choir at the time of the shooting.

Monnat said in early May that Tiller had asked federal prosecutors to step up investigations of vandalism and other threats against the clinic out of fear that the incidents were increasing and that Tiller's safety was in jeopardy. However, Stolz said authorities knew of no threats connected to the shooting.

Adam Watkins, a 20-year-old who said he has attended the church his entire life, said he was sitting in the middle of the congregation when he heard a small pop at the start of the service.

"We just thought a child had come in with a balloon and it had popped, had gone up and hit the ceiling and popped," Watkins said.

Another usher came in and told the congregation to remain seated, then escorted Tiller's wife out.

"When she got to the back doors, we heard her scream, and so we knew something bad had happened," Watkins said.

Church members said anti-abortion protesters have shown up outside the church on Sundays regularly.

"They've been out here for quite a few years. We've just become accustomed to it. Just like an everyday thing, you just looked over and see them and say, 'Yup they're back again.'"

He added: "We had no idea that someone would come into our church and do such a bad thing like that — inside of a church."

The last killing of an abortion doctor was in October 1998 when Dr. Barnett Slepian was fatally shot in his home in a suburb of Buffalo, N.Y. A militant abortion opponent was convicted of the murder.

Federal marshals protected Tiller during the 1991 Summer of Mercy protests, and he was protected again between 1994 and 1998 after another abortion provider was assassinated and federal authorities reported finding Tiller's name at the top of an assassination list.

One of Tiller's lawyers and friends, Dan Monnat, told ABC's "Good Morning America" that Tiller had been supported by his wife and children in his decision to continue providing abortion services.

"If Dr Tiller is not going to service a woman's right to chose, who will do it?" Monnat said.

"Many of those have been terrorized and run off by protesters," he said about other abortion providers.

One of the few remaining late-term abortion clinics is in Boulder, Colo., where Dr. Warren Hern denounced Tiller's killing as the "inevitable and predictable consequence of decades of anti-abortion" rhetoric and violence.

"Dr. Tiller's assassination is not the lone and inexplicable action of one deranged killer," Hern said Sunday. "This was a political assassination in a historic pattern of anti-abortion political violence. It was terrorism." I'm confused. If the shooter might have a possible connection to an anti-abortion group, wouldnt shooting the doctor have an OPPOSITE affect to his cause?